Method of manufacturing permanent magnets from an iron-base alloy containing ni, al, and co as principal elements



Feb. 4, 1958 A. J. J. KOCH El 2,821,759

- METHOD OF MANUFACTURING PERMANE MAGNETS FROM AN IRON-BASE ALLOY CONTAINING m, A;

AND 0 PRINCIPAL ELEMENTS Fi 1m. 11, 1953 IN VEN TORS ADOLF JOHANNES JACOBUS KOCH EDUARD MARIA HENRICUS LIPS KRIJN JACOBUS DE VOS AGENT METHOD OF MANUFACTURING PERMANENT MAGNETS FROM AN IRON-BASE ALLOY CON- TAINING Ni, Al, AND C AS PRWEEPAL ELE- MENTE Adolf .lohannes Jacobus Koch, Eduard Maria Henricus Lips, and Krijn Jacobus de Vos, Eindhoven, Netherlands, assignors, by mesne assignments, to North American Philips Qompany, Inc., New York, N. Y., a corporation of Delaware Application December 11, 1953, Serial No. 397,658

Claims priority, application Netherlands December 17, 1952 3 Claims. (Ci. 22-213) The invention relates to a method of manufacturing magnetically anisotropic permanent magnets from an iron base alloy containing nickel, aluminium and cobalt as principal elements. The crystals in the magnet are predominantly orientated so that the [100] direction is substantially parallel to the magnetic preferred direction in which the magnet is magnetized. According to this invention during solidification of the magnet the heat dissipation at the part situated between the two pole faces is retarded, at least one, preferably both ends being cooled, and is further characterized in that during the casting process the alloy is supplied to a part of the mould which preferably lies approximately in the middle of the magnet and which extends at least substantially throughout the outer circumference of the magnet to form thereby an annular part surrounding the magnet near its center.

It has been found that thus a satisfactory crystal orientation is obtainable in a simple manner.

In a preferred embodiment of the invention the height of the said annular part of the mould adjacent the remainder of the magnet is from /s to /2 of the length of the magnet and the dimensions in diametrical directions are from /s to /2 of the dimensions of the remainder of the magnet.

The invention will now be described with reference to the accompanying diagrammatic drawing in which an embodiment thereof is shown by way of example.

Referring now to the single figure of the drawing, a part 1 of the mould consisting of moulding sand is arranged on a cooling plate 2, a cooling plate 3 covering the mould. Pouring the alloy in the aperture 4 results in a magnet 5, the heat dissipation being retarded during the solidification process by an annular part 6 surrounding the magnet, so that the desired crystal orientation is obtainable in the magnet 5. After cooling the annular part 6 can be removed so that the final magnet is left.

The height 7 of the annular part adjacent the magnet is preferably ca. /3 of the length 8 of the magnet, the dimensions 9 in diametrical directions each being ca. of the diameter 10 of the remainder of the magnet.

What is claimed is:

1. In a method of manufacturing a magnetically anisotropic magnet from an iron base alloy containing as prin cipal elements Ni, Al, and C0, the steps comprising introducing said alloy in a molten state into a mold of a heat retardant material having a central annular reatent O "ice cessed portion, said molten alloy being introduced into the mold through an aperture connecting directly with said annular recessed portion, placing cooling plates in thermal contact with both ends of said molten alloy to extract heat therefrom in one direction while heat loss is retarded in a transverse direction by an annular ring of metal formed in said recessed portion, whereby a casting is obtained after cooling which contains crystals predominantly oriented in the direction.

2. In a method of manufacturing a magnetically anisotropic magnet from an iron base alloy containing as principal elements Ni, Al, and Co, the steps comprising introducing said alloy into a mold of a heat-retardant material having a central annular recessed portion surrounding a cavity of given height and width dimensions in which the molten metal is received, said recessed portion having a height dimension which is about A5 to /2 the height dimension of said cavity and a width dimension about /5 to /2 that of said cavity, said alloy being introduced into the mold through an aperture connecting directly with said annular recessed portion, placing cooling plates in thermal contact with both ends of said molten alloy in said cavity to extract heat therefrom in one direction while heat loss is retarded in a transverse direction by an annular ring of metal formed in said recessed portion whereby a casting is obtained after cooling which contains crystals predominantly oriented in the [100] direction.

3. In a method of manufacturing a magnetically anisotropic magnet from an iron base alloy containing as principal elements Ni, Al, and Co, the steps comprising introducing said alloy in a molten state into a mold of a heat-retardant material having a central annular recessed portion surrounding a cavity of given height and width dimension in which the molten alloy is received, said recessed portion having a height dimension which is about /3 the height dimension of said cavity and a width dimension about A that of said cavity, said alloy being introduced into the mold through an aperture connecting directly with said recessed portion, placing cooling plates in thermal contact with both ends of said molten alloy in said cavity to extract heat therefrom in one direction while heat loss is retarded in a transverse direction by an annular ring of metal formed in said recessed portion whereby a casting is obtained after cooling which contains crystals predominantly oriented in the [100] direction, and removing the annular metal ring from said casting.

References Cited in the file of this patent UNITED STATES PATENTS 2,052,921 Dockray et al Sept. 1, 1936 2,497,210 Day Feb. 14, 1950 2,578,407 Ebeling Dec. 11, 1951 FOREIGN PATENTS 619,991 Great Britain Mar. 17, 1949 652,022 Great Britain Apr. 11, 1951 661,727 Great Britain Nov. 28, 1951 684,522 Great Britain Dec. 17, 1952 OTHER REFERENCES Casting and Forming in Manufacturing (Campbell), published by McGraw-Hill Book Co., New York, N. Y., 1950 (pages 66-67). 

1. IN A METHOD OF MANUFACTURING A MAGNETICALLY ANISOTROPIC MAGNET FROM AN IRON BASE ALLOY CONTAINING AS PRINCIPAL ELEMENTS NI, AL, AND CO. THE STEPS COMPRISING INTRODUCING SAID ALLOY IN A MOLTEN STATE INTO A MOLD OF A HEAT RETARDANT MATERIAL HAVING A CENTRAL ANNULAR RECESSED PORTION, SAID MOLTEN ALLOY BEING INTRODUCED INTO THE MOLD THROUGH AN APERTURE CONNECTING DIRECTELY WITH SAID ANNULAR RECESSED PORTION, PLACING COOLING PLATES IN THERMAL CONTACT WITH BOTH ENDS OF SAID MOLTEN ALLOY TO EXTRACT HEAT THEREFROM IN ONE DIRECTION WHILE HEAT LOSS IS RETARDED IN A TRANSVERSE DIRECTION BY AN ANNULAR RING OF METAL FORMED IN SAID RECESSED PORTION, WHEREBY A CASTING IS OBTAINED AFTER COOLING WHICH CONTAINS CRYSTALS PREDOMINANTLY ORIENTED IN THE (100) DIRECTION. 